TWI468473B - Uv curable ink with improved adhesion - Google Patents

Description

UV curable ink with improved adhesion

The present invention relates to an ultraviolet curable ink having improved adhesion.

Background of the invention

The inks used in the ink jet printing industry are typically liquid dispersions, solutions or latexes. Known ink types include oil based inks, non-aqueous based inks, water based inks, and solid inks. The ink jet method includes spraying a small ink droplet from a printhead onto a print medium at an orifice. Then, the small droplets placed are stably dried using, for example, heat or driven air, or allowed to dry in the surrounding environment.

Recently, the manner in which ink is cured by light radiation (and especially ultraviolet (UV) curing) has become popular. In these cases a special optical radiation curable ink is used and the image is cured by exposure to a source of optical radiation. The term "curing" as used in the context of this application refers to the conversion of a liquid such as an ink into a solid by exposure to actinic radiation. The use of optical radiation curable inks and this curing method is rapidly becoming an alternative to current conventional drying.

A problem with the use of many types of inks is that they are less susceptible to attachment to non-porous or low surface tension substrates such as polypropylene, vinyl, polyolefins, and the like. For example, polypropylene is widely used in the display of fixed and semi-fixed point of sale. Because of the surface of the polypropylene It is less active and has a lower surface tension, so polar solvents such as acrylic monomers cannot be wetted. As a result, it produces a poor adhesion. Further, when printing is performed on the other ink tip, an appropriate bonding between the ink layers on the substrate may become lower than the desired effect depending on the amount of ink loaded. Moreover, when referring to particular ultraviolet curable inks, these inks are typically prepared using oligomers such that the ink has a higher viscosity than typical solvent or water based inks. Spraying such viscous inks has the difficulty of facing it, and further typically requires spraying at a lower frequency, resulting in a slower printing speed. Because these inks are more viscous, they are typically also sprayed at higher temperatures (e.g., above about 40 ° C). This higher temperature can provide some control over the otherwise highly viscous inks, but can adversely affect the life of the structure including the printhead. Therefore, in the field of ultraviolet curable inks, particularly in the problems associated with adhesion to polypropylene or other non-porous, low surface tension substrates, there is still significant room for improvement.

In accordance with an embodiment of the present invention, a photocurable ink composition for ink jet printing having improved adhesion to a non-porous, low surface tension substrate comprising: a liquid carrier liquid is specifically proposed Once polished pigment, a photoinitiator and a halogenated polyolefin.

In accordance with an embodiment of the present invention, an inkjet ink printing system is specifically provided comprising: a) a non-porous, low surface tension media matrix; b) at least one photocurable inkjet ink comprising: i) a liquid carrier liquid, Ii) a ground pigment, iii) a photoinitiator, and iv) a halogenated polyolefin; and c) a source of light energy that is structured to be sprayed once the inkjet ink is printed on a substrate The ink ink applies light energy having a frequency and energy level suitable for photocuring the inkjet ink.

Detailed description of the preferred embodiment

Before the present invention has been disclosed and described, it is understood that the invention is not limited to the specific methods and materials disclosed herein. It is also to be understood that the terms of the invention are intended to be limited to the specific embodiments and are not intended to To define it.

In the scope of the patent describing and claiming the invention, the following terms will be employed.

The singular forms "a", "the", "the" and "the" are meant to include the plural. Thus, for example, reference to "a pigment" is meant to include one or more of these materials.

The term "curing" refers to a process of converting a liquid, such as an ink, into a solid by exposure to actinic radiation such as, for example, optical radiation (for example, ultraviolet light).

The terms "non-porous" or "low surface tension" may be used interchangeably and, when they represent a matrix such as a vehicle matrix, include relatively poor water permeability, absorbency, and/or adsorptivity. surface. Vinyl and other plastic sheets or films, metals, coated offset media, glass And other similar matrices are considered to be non-porous. According to these definitions, a photocurable ink composition for ink jet printing having better adhesion to a non-porous, low surface tension matrix may comprise a liquid carrier liquid, and a grinding solvent (eg, triethyl ethane). A ground pigment, a photoinitiator, and a halogenated polyolefin (e.g., chlorinated polypropylene) milled in diol divinyl ether (DVE-3).

In another embodiment, the inkjet printing system can comprise a non-porous or low surface tension matrix such as polypropylene, a photocurable inkjet ink, and a structure to be printed on the inkjet ink. When on the non-porous substrate, a source of light energy is applied to the light energy. The light energy can include UV, IR, and/or visible light. More specifically, the light energy can have a frequency and energy level suitable for curing the photocurable inkjet ink. The inkjet ink can comprise a liquid carrier liquid, a ground pigment, a photoinitiator, and a halogenated polyolefin.

In another embodiment, the method of printing an image may include spraying a curable inkjet ink onto a non-porous or low surface tension matrix such as polypropylene, or various other plastic and plastic derivatives. on. The photocurable inkjet ink can comprise a liquid carrier liquid, a ground pigment, a photoinitiator, and a halogenated polyolefin. Another step includes applying light energy thereto when the photocurable inkjet ink is printed on a substrate, wherein the light energy has a frequency and energy suitable for curing the photocurable inkjet ink. size. It should also be noted that these inks can also be used to print on porous substrates by using such systems and methods on, for example, non-porous substrates or low surface tension substrates.

In accordance with the teachings of the present invention, since the ink systems are typically photocurable, in accordance with some embodiments of the present invention, the curing light radiation may be ultraviolet light, and the ink used for printing may comprise an ultraviolet activation initiation. Ultraviolet (UV) curable ink for agents (also known as UV starters). For example, in these examples, the curing optical radiation can be ultraviolet light radiation emitted by an ultraviolet lamp, blue laser light, ultraviolet laser light, or ultraviolet LEDs. According to some embodiments of the invention, the curing light radiation can be provided by a source of ultraviolet light that operates in a continuous mode. According to other embodiments of the invention, the curing light radiation can be provided by a source of ultraviolet light that operates in a flashing or pulsed mode. After understanding the disclosure of this case, those skilled in the art will know that other methods of applying ultraviolet radiation can also be applied. It is stated that it may also be used to include other curing systems other than the ultraviolet curing system (e.g., IR or visible light systems) as long as the optical radiation used is suitable for initiating the curing process of the inkjet ink.

Some specific examples of the invention are either various photocurable compositions comprising an ink jet recording liquid. Therefore, the ink composition may contain an oligomer, a multifunctional acrylate, and a urethane acrylate. Further, the ink composition may comprise an acrylate mixture which is capable of undergoing polymerization under ultraviolet curable light radiation in the presence of an ultraviolet activator. Non-limiting specific examples of the ultraviolet activation initiator may include an α-aminoketone photoinitiator having or not having a sensitizer such as Darocur ITX (2-isopropylthioxanthone), such as Ciba Irgacure 907, Ciba Irgacure 369 and Ciba Irgacure 379; bisacylphosphine oxide (BAPO) Ultraviolet light initiators such as Irgacure 907 or Irgacure 819, Darocur 4265 and Darocur TPO; alpha-hydroxy ketone ultraviolet light initiators such as Irgacure 184 and Darocur 1173. With regard to the acrylate, these compositions can be used as some highly reactive acrylates. In addition, some acrylates such as monoacrylates have good solubility, high flexibility, and low glass transition temperature (Tg). A lower Tg at room temperature can improve the flexibility of the ink layer. For example, in one embodiment, a monoacrylate having a Tg of less than about 30 ° C or 40 ° C can be used to improve the flexibility of the ink layer compared to the same ink without the monoacrylate. .

Monoacrylate has good adhesion to plastics and can provide high flexibility, so that the adhesion to plastic can be improved even when the plastic is bent. Some monoacrylates can modify or swell specific plastic matrices as well as other non-porous, porous and/or low surface tension matrices such as polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and polyolefins. . The modification or swelling of this matrix can also improve adhesion. For example, other acrylates of triacrylate can result in low shrinkage, good reactivity, improved mechanical properties, and chemical resistance of the ink. For example, the higher the molecular weight, the lower the crosslink density and the shrinkage. The lower the rate. Still further, some acrylates such as diacrylates have higher solvency and higher reactivity for non-porous surfaces. This is illustrated by the fact that any suitable combination of acrylates or acrylates can be used to achieve a balance of these or other properties. Moreover, although the scope of the invention is not limited in this respect, the acrylates may also be modified or derivatized acrylates. Specific examples of such include polyether Alkyl alcohol acrylate, polyether acrylate oligomer, cyclohexane trimethylolpropane acetal acrylate (CTFA) or amine acrylate. In particular, acrylates such as CN386 and Genomer 5275 can be used to improve the bond between the layers of the printed inkjet ink and the effect of attaching to a non-porous substrate during printing.

The relative amounts of the different components in the ink jet recording composition can be varied. For example, the relative amount of the phase photoinitiator can range from about 0.1 wt% to about 8 wt%, and in another embodiment, from about 0.1 wt% to about 4 wt%. In other embodiments, the relative amount of the photoinitiator can range from about 0.2 wt% to about 2 wt%, or even from about 0.2 wt% to about 1 wt%. In other embodiments, the relative content of the halogenated polyolefin can range from about 0.5 wt% to about 4 wt%, or even from about 1 wt% to about 2.5 wt%. Likewise, the relative amounts of various other ingredients may be present between 1 wt% and 30 wt%. For example, the acrylate can be present from 1 wt% to 8 wt%. Alternatively or additionally, a relative amount of from 5 wt% to 25 wt% of vinyl caprolactam can be used to also improve the adhesion of the ink layer to the substrate.

The ingredients may further comprise any coloring agent such as, for example, a pigment which is ground pigment, and optionally an additive such as a dispersing agent, a wetting agent, a surfactant, a leveling agent, and the like. . Non-limiting specific examples of pigments that can be used in the formulation of a typical embodiment of the present invention include E4 GN Yellow 150, RT-355-Red Violet, Hostaperm Blue P-BFS Blue Green, Sunfast Black 7, PV Fast Blue BG, PV fast red E5 B, PV fast yellow HG, timeless black R30, other pigments or a mixture of some pigments. More specifically, the black and dye pigments used in the present invention are not particularly limited, and inorganic pigments or organic pigments can be used. Suitable inorganic pigments include, for example, titanium oxide, cobalt blue (CoO-Al ₂ O ₃ ), chrome yellow (PbCrO ₄ ), and iron oxide. Suitable organic pigments include, for example, azo pigments, polycyclic pigments (for example, cyanine pigments, lanthanide pigments, perynone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments). , thiopurine dye, isoindolinone pigment and quinophthalone pigment), dye chelates (for example, basic dye type chelates and acid dye type conjugates), nitro pigments, Nitrochromes and analogs thereof. Non-limiting specific examples of dispersing agents which may be used in the formulation of typical embodiments of the present invention together with these or other pigments include Solsperse 32000, Solsperse 39000, Solsperse 5000, Solsperse 22000, Disperbryk 163, Disperbyk 167, Disperbyk 168, Disperbyk 180, Disperbyk 190, Disperbyk 191, or the like.

As mentioned, the inkjet ink composition can also optionally include a wetting agent. Non-limiting specific examples of such wetting agents may include organic anthraquinone polyether acrylates such as Tego Rad 2200 N, Tego Rad 2300, and Byk 358N. The ink may also include a poly-dimethyl-decane ane wetting agent such as Byk 333, Byk 307, and Silwet L-7604. If a wetting agent is used, it can be present from 0.01% to about 10% by weight of the inkjet ink composition.

One of the unique characteristics of the photocurable ink of the present invention is its improved adhesion to non-porous and low surface tension media substrates such as plastics. Sex. These inks are such that they can be structured by means of a halogenated polyolefin such as chlorinated polypropylene, after being sprayed onto a non-porous, low surface tension substrate, allowing the substrate to adhere to the ink. . As described therein, the inkjet ink composition can be shot onto a media substrate. Moreover, the systems and methods of the present invention can include the media matrix. The media matrix used in the present invention comprises a non-porous and low surface tension media matrix. Non-limiting specific examples thereof include plastic, PVC, labelled paper and polypropylene, and synthetic paper such as Yupo synthetic paper. The banner strips are specifically structured to print a logo that has a smooth surface and is typically designed for color printing. Yupo synthetic paper is a specific example of synthetic paper. Yupo is a specific type of waterproof, anti-pollution, strong and durable polypropylene.

The photocurable inks of the present invention are not limited to some polyolefin types. Non-limiting specific examples of the halogenated polyolefin may include chlorinated polyethylene, chlorinated polypropylene, chlorinated polybutene, brominated polyethylene, brominated polypropylene, brominated polybutene, fluorinated polyethylene, fluorine Polypropylene and fluorinated polybutene. Thus, as shown in these specific examples, although chlorine is preferred for use in the present invention, other halogens having similar chemical properties that are compatible with the teachings of the present invention can be utilized. Non-limiting specific examples thereof are bromine or fluorine.

Another unique feature of the photocurable inks of the present invention is that they can be prepared such that they are even high jetting frequencies, for example, greater than 18-20 kHz, greater than 25 kHz, or even greater than 29 kHz. Underneath, it is possible to remove air from the ink before and/or during use. As noted The fact that these inks can be ejected at higher frequencies does not limit these inks to higher injection frequency systems. These inks can also be ejected at relatively low frequencies. This is illustrated by the fact that, in general, in ultraviolet light and other photocurable inks, such inks are typically characterized by affecting the gas content of the ink jet process. The ink of the present invention may be characterized in that it has an abnormally low gas content. In some embodiments, the method for grinding the pigment can achieve these advantages. For example, by grinding the pigment with a specific solvent, the generation or release of air or gas can be minimized or eliminated. A specific example of a suitable solvent for achieving this purpose may be triethylene glycol divinyl ether (DVE-3), which allows the print head to be degassed without prior ink. Operate at higher injection frequencies. It is worth noting that DVE-3 is only one specific example of this solvent, and other solvents can provide a similar function depending on the pigment. Thus, other solvent selections for milling can be used in accordance with specific embodiments of the present invention. In one aspect of the invention, the pigment and the grinding solvent can be selected such that they are relatively less reactive with respect to each other, or the solvents can be selected such that the pigment particles have minimal or even no dissolution. gas. It is also worth noting that conventionally known ultraviolet inks typically have an amount of dissolved oxygen between 6 and 8 ppm by weight of the ink, whereas the present invention uses a pigment such as DVE-3 which has a low gas solvency of a grinding solvent. The ink may have, for example, an amount of dissolved oxygen of less than 5 ppm between 3 and 5 ppm by weight which will reduce the reactivity of the ink.

Typically, in order to produce a complete color image, the ink set may comprise an inkjet ink composition having cyan, magenta, and yellow, or It is a composition of inkjet inks of cyan, light cyan, magenta, bluish-purple, and yellow. Black ink can also be included in these ink sets. Other combinations are also possible.

Specific example

In the specific examples of the following ink compositions, the components are indicated by the sub-weight percentages shown. It is to be noted that the following specific examples are not intended to limit the scope of the invention in any way. It is to be noted that the following specific examples are illustrative of specific examples of the present invention that are currently known to be optimal. However, it should be understood that the following description is merely exemplary or illustrative of the application of the principles of the invention. Modifications and substitutions of many components, methods and systems may be made without departing from the spirit and scope of the invention. The accompanying patent application scope is intended to cover such modifications and structures. Therefore, when the present invention is specifically described above, the following specific examples may further provide details of the specific examples which are currently considered to be the most feasible and best of the invention.

Specific example 1

Specific example 2

Specific example 3

Concrete example 4

According to a typical embodiment of the invention, the ink formulation is applied to a polypropylene substrate and cured with ultraviolet light at about 200 mj/cm ² . The thickness of the ink layer is approximately 12.5 microns. The ink has a viscosity of less than 30 cp, a surface tension of 26.9 dynes/cm, and a particle size of less than 1 micron. The cured ink layer does not exhibit ink flaking or chipping, and can withstand standard abrasion and tape adhesion tests.

While certain features of the invention have been shown and described, Therefore, it is to be understood that the appended claims are intended to cover such modifications and variations that fall within the spirit of the invention.

Claims (12)

A photocurable ink composition for ink jet printing having improved adhesion to a non-porous, low surface tension matrix, comprising: a liquid carrier liquid, the ground pigment is attached to the ground pigment Grinding, a photoinitiator, and a halogenated polyolefin are included in a grinding solvent comprising triethylene glycol divinyl ether; wherein the photocurable ink composition has a dissolved oxygen content of less than 5 ppm by weight. The composition of claim 1, wherein the composition comprises a monoacrylate having a glass which can improve the flexibility of the ink layer as compared with the same ink prepared without the monoacrylate. Conversion temperature (Tg). The composition of claim 1, wherein the composition comprises an amino acrylate. The composition of claim 1, wherein the halogenated polyolefin is a monochlorinated polyolefin. The composition of claim 1, wherein the halogenated polyolefin comprises chlorinated polypropylene. An inkjet ink printing system comprising: a) a non-porous, low surface tension media matrix; b) at least one photocurable inkjet ink comprising: i) a liquid carrier liquid, Ii) once the pigment is ground, the ground pigment is ground in a grinding solvent comprising triethylene glycol divinyl ether, iii) a photoinitiator, and iv) a halogenated polyolefin, wherein the photocurable ink The composition has a dissolved oxygen content of less than 5 ppm by weight; and c) a source of light energy that is configured to apply light energy to the inkjet ink once the inkjet ink is printed on a substrate, The light energy has a frequency and energy level suitable for curing the photocurable inkjet ink. A system as claimed in claim 6 wherein the system comprises two photocurable inkjet inks, each of which has a different hue or color density than the other. The system of claim 6, wherein the at least one photocurable inkjet ink comprises an amino acrylate in an amount to improve the printed photocurable inkjet ink layer. Adhesion between. The system of claim 6 wherein the at least one photocurable inkjet ink comprises at least one of vinyl caprolactam and an acrylate. The system of claim 6 wherein the halogenated polyolefin is selected from the group consisting of monohalogenated polyethylene, monohalogenated polypropylene, and monohalogenated polybutene. The system of claim 6 wherein the halogenated polyolefin comprises chlorinated polypropylene. A system of claim 6 wherein the media matrix is a plastic matrix.